Lubricating oil additives



LUBPJCATHNG OIL ADDETEV Edward L. Cole, Glenham, and William E. Shelton, Beacon, N. Y., assignors to The lexas Company, New York, N. Y., a corporation of Delaware No Drawing. Application September 16, 1954,

Serial No. 456,604

3 Claims. or. zen-4s This invention relates to additives for mineral lubrieating oils and more particularly to additives for improving viscosity index, anti-oxidant and anti-varnishing characteristics of such oils.

The additives of this invention consist essentially of oil-soluble isobutylene-polyene hydrocarbon-hydrogen sulfide polymer containing 0.5 to weight percent sulfur, having average molecular Weight between about 2000 and about 7000, and prepared by polymerizing with Friedel-Crafts type catalyst a major molal proportion of isobutylene with a minor molal proportion of polyene hydrocarbon, and hydrogen sulfide in less than the theoretical amount necessary to saturate the double bonds in the isobutylene and the polyene hydrocarbon reactants.

The addition of the polymer to mineral lubricating oil fraction effects a substantial improvement in viscosity index of the resulting lubricant, and, in addition, imparts excellent anti-varnishing and superior anti-oxidant characteristics to the lubricant. The novel lubricant compositions of this invention comprise 80 to 99.5% mineral lubricating fraction and 0.5 to of the polymer. The novel lubricant compositions of this invention are char acterized by excellent viscosity-temperature properties as illustrated by the fact that they possess very high V. I.s, e. g. over 100, and are extremely resistant to oxidation and to varnish formation.

T he excellent anti-oxidant properties of the novel lubricant compositions of this invention are demonstrated in the MacCoull corrosion test. The anti-varnishing characteristics of the lubricant compositions are demonstrated by their response to the Toettcher varnish test, described hereinafter.

In the Toettcher varnish test, which was recently developed in this laboratory to evaluate the varnish-forming tendencies of lubricating oils, there is employed the Mac- Coull corrosion machine modified by the elimination of Micarta bushings, Cu- Pb bearing specimen and copper battles, and by the addition of a Pyrex glass cylinder and by a smaller size copper bafitle. Test oil in the amount of 140 ml. is added to each beaker containing a brass plate to which is attached a smaller copper battle on a glass ringjthe oil is stirred in the beaker for 13 hours at 350 F.; at the conclusion of this time the tared glass ring is removed, rinsed in precipitation naphtha, oventreated at 220 F. for 3 to 4 hours, passed into a desiccator to cool to room temperature, and reweighed. The increase in weight in the ring indicates the amount of varnish deposited, and the following scale is used as a criterion:

Increase in weight, milligrams: Remarks 14 Low varnish.

58 Low-medium varnish. 9-16 Medium varnish. 17-24 Medium-heavy varnish.

and over Heavy varnish.

2,799,557 Patented July 16, 1957 Generally no more than about 10% of the polymer is employed in the lubricant composition of the invention because such a substantial improvement in the properties of the lubricant composition is effected by the presonce of small quantities of the polymer. As a consequence, the lubricant compositions of this invention usually comprise to 99.5% mineral lubricating fraction and 0.5 to 5% of the polymer. It is also possible to incorporate other additives to the novel lubricant compositions of this invention.

Use of the polyene hydrocarbon, e. g. a dior tri-olefin, in the polymer especially enhances the anti-oxidant characteristics which the polymer imparts to a mineral lubricating oil with which it is compounded. The physical nature of the polymer is responsive also to changes in proportion of polyene hydrocarbonzisobutylene used. Thus, increasing the proportion of polyene hydrocarbon relative to that of isobutylene in the preparation of the polymer tends to make the polymer stiffer while decreasing the proportion of polyene hydrocarbon tends to make the polymer more liquid. However, polymers made by use of molal proportions of isobutylenezpolyene hydrocarbon substantially above about 2021 appear to be less efiective asan anti-oxidant for lube oil than those made by use of a greater molal proportion of polyene hydrocarbon; therefore, use of molal proportions of isobutylenezpolyene hydrocarbon less than about 20:1 are preferred for the polymerization. The polyene hydrocarbon can be, for example, butadiene 1,3; butadiene 1,2; 1,2 pentadiene; 1,3 pentadiene; 1,4 pentadiene; 2,3 pentadiene; 3-methyl-1,2 butadiene; isoprene; 1-2 (3,4) hexadienes; 1,3,5 hexatriene; 1,3,5 heptatriene; 2,5-dimethyl- 1,3,4-hexatriene; 1,3 cyclopentadiene; methyl cyclopentadiene; 1,3-cyclohexadiene; and 2 methyl-1,3 cyclohexadiene.

For efiiciency and economy in the preparation of polymer of our invention the preferred polyene hydrocarbon is a diolefin, particularly butadiene 1,3. Most advantageously the molal proportions of isobutylenezdiolefin hydrocarbon used are in the range from 2:1 to 15:1.

Hydrogen sulfide is added to the reaction mixture in amount less than the theoretical amount necessary to saturate every olefinic double bond in both the isobutylene and the polyene hydrocarbon as fed to the reactor. Preferentially, the amount of hydrogen sulfide added is about 0.05 to about 0.8 mol per each such olefinic double bond. The preferred catalyst for preparation of the polymer is aluminum chloride; aluminum bromide, titanium tetrachloride and boron trifluoride also can be used as catalysts in the polymerization. Useful mol ratios of catalystftotal isobutylene and polyene hydrocarbon employed are broadly between about 0.001:1 and about 0.04:1. The preferred polymers, i. e. the superior antioxidant additives for lube oil, are prepared using mol ratio of catalystztotal hydrocarbon between about 0.02 and about 0.03, and have estimated average molecular weight between about 3000 and about 4000 (Staudinger method).

Polymer of the type described is prepared advantageously by polymerizing in the presence of an aluminum chloride catalyst isobutylene With 'butadiene and hydrogen sulfide using these approximate mol ratios4 isobutylenezl butadienez4 hydrogen sulfide. The reaction mixture can be diluted with solvents such as ethyl chloride or pentane if desired. However, we have found that the polymers formed without diluents are generally superior lube oil additives and, therefore, prefer to use no diluents in the reaction.

and about 7000.

Broadly average molecular of.

In the initial stages of the polymerization, temperatures below 75 F. are used. At least part of, e. g. at least one third of, advantageously about one half or all, the hydrogen sulfide charge is added to a mixture of the hydrocarbon reactants and catalyst, which mixture has been maintained agitated at these low temperatures for about Mi-6, and preferably 1 /2-4 hours. it has been found that the polymers prepared using initial temperature in the range of plus 30 F. to minus 100 F. are particularly effective additives for making the superior lubricant compositions of this invention. After at least part of the hydrogen sulfide has been added to the reaction mixture, elevated temperatures, e. g. about 100 F. and even higher, can be employed. By addition of hydrogen sulfide in this manner polymers in the desired average molecular weight range are formed very eificiently from the hydrocarbons charged. Pressures ranging from atmospheric to superatmospheric of atmospheres can be employed in the formation of the polymer. The polymerization is effected in an autoclave at autogeneous pressures.

Sulphur content of the resulting polymer falls in the range of 0.5 to 15 weight percent and usually is about 2 to 8 weight percent. The hydrogen sulfide appears to play an active role during formation of the product to introduce sulfur into the polymer in various forms such as sulfide groups, sulfur cross linkages and alkyl sulfide side chains. However the polymer, which is free of mercaptan odor, shows only a trace of sulfur in mercaptan form upon infra-red analysis.

By varying ratio of polyene hydrocarbon to isobutylene a variety of additives can be made without having to maintain inventory of a great diversity of raw materials; thus it is possible to tailor-make with facility additives for imparting similar characteristics to a variety of oils or for imparting diverse characteristics to the same oil stock.

The following examples show ways in which our polymers have been prepared and evaluated, but are not to be construed as limiting the invention. All parts expressed are parts by weight.

Example 1.Thirty-five parts of aluminum chloride were charged to a side-stirred steel reactor cooled to minus 28 F. 486 parts (8.69 mols) of isobutylene and 114 parts (2.15 mols) of butadiene 1,3 were then added and the mixture stirred for 4 hours at minus F. to minus F. 159 parts (4.68 mols) of hydrogen sulfide were added and stirring was continued for 16 hours at 13 F., then for 2 hours at 284-304 F. The mixture was cooled and 148 parts (4.36 mols) of hydrogen sulfide were added thereto, then stirring was conducted overnight at 80 F. to 97 F. whercafter the reaction mixture was poured into pentane. The amount of hydrogen sulfide used was about 70% of the theoretical for saturation of the double bonds in the isobutylene and the diolefin reactants. The solid precipitated phase was separated from the pentane mixture by decantation. An aliquot of the pentane solution was water washed, and distilled to 310 F. at 5 mm. to remove pentane. The bottoms obtained from this distillation were the polymer which analyzed 2.53% by weight sulfur. The polymer was a highly viscous brown transparent liquid. Average molecular weight was estimated to be about 80 (Staudinger). 1.5 parts of the polymer obtained was dissolved in 7 parts of benzene for blending of the polymer with lubricating oil. Yield of the polymer was 95% based on isobutylene and butadiene used.

The excellent qualities of lubricant compositions comprising lubricating oil fraction and the polymer obtained as described above are illustrated in Table 1, below, wherein the properties of 20 grade paraffin base oil are compared with a lubricant composition comprising 20 grade parai'iin base oil and 1.5 percent by weight of the above-described polymer.

Table I 20 grade oil Polymer in 20 grade oil 8.5 (54.2 SUS). 10.60 (61.3 808). Viscosity index 92 103.5. MacOoull Corr. at 350 F.:

Wt. Loss, mgJlO hrs 1-3. Neut. No. (S)

Vis.i SUS 210 ll, of used o Toettcher Varnish at 350 F.:

Varnish Wt, Mg./13 hrs Neut. No. (S) 6 Vis., SUS at 210 F 26.7-29.9 (heavy varnish).

1.4-2.0 (10w varnish).

The anti-oxidant properties as illustrated by the above MacCoull corrosion test results and the anti-varnishing characteristics as indicated by the above Toettcher varnish test results are particularly significant. In addition, the improvement in viscosity index of the 20 grade oil obtained by the addition of the polymer is very good.

Example 2.35 parts of aluminum chloride were charged to a side-stirred steel reactor cooled to minus 25 F. 560 parts (9.96 mols) of isobutylene and 67 parts (1.24 mols) of butadiene 1,3 were then added and the mixture stirred for 3 hours at minus 16 F.'to minus 44 F. 300 parts pentane and 150 parts hydrogen sulfide (4.4 mols) were then added at plus 4 F. Reaction mixture was stirred overnight at 22-70 F., then for 8 hours at 2l5-298 R, whereafter the reaction mixture was poured into pentane. The amount of hydrogen sulfide used was about 0.35 mol per double bond in the isobutylene and diolefin reactants. The solid precipitated phase was separated from the pentane mixture by decantation. The pentane solution was neutralized, water washed and distilled to 310 F, at 5 mm. The bottoms obtained from this distillation were the polymer which contained a substantial percentage of sulfur. The polymer was a highly viscous, brown transparent liquid. Average molecular weight was estimated to be about 3000 (Staudinger). Yield of the polymer was 95.5% based on isobutylene and butadiene used.

2 /2 parts of the above polymer were blended with 97 /2 parts of an S. A. E. 8 grade oil which had a V. I. of 95. The resulting lubricant composition had a Kin. Vis. of 42.6 and 6.5 at 100 and 210 F., respectively, and a V. I. of 112.5.

1.5 parts of the above polymer were blended with 98.5 parts of 20 grade oil. The excellent anti-varnishing character of this lubricant composition is illustrated in Table II wherein there are compared the results obtained by the T oettcher varnish test on the 20 grade oil alone and on this lubricant composition.

Obviously any modifications and variations of the invention as herein above set forth may be made without departing from the spirit and scope thereof and, there fore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. An additive for mineral lubricating oil consisting essentially of an oil soluble isobutylene-butadiene'hydrd gen sulfide polymer containing 0.5-15 weight percent sulfur, having average molecular weight between about 2000 and about 7000, and prepared by polymerizing, in a reactor with Friedel-Crafts catalyst, from 220 mols of isobutylene with a mol of butadiene and about 0.05 to about mol of butadiene and about 0.05 to about 0.8 mol of 10 hydrogen sulfide per olefinic double bond in said hydrocarbon reactants as fed to the reactor.

3. The lubricant composition as described in claim 2 wherein the catalyst used is one selected from the group consisting of aluminum chloride, aluminum bromide, 15

boron trifiuoride, and titanium tetrachloride; the mol ration of isobutylene:butadienezhydrogen sulfide used in preparation of the polymer is about 4:1:4; and the polymer comprises 0.5 to 5% of the total lubricant compo- 5 sition.

References Cited in the file of this patent UNITED STATES PATENTS 2,296,399 Otto et a1. Sept. 22, 1942 2,312,750 Cohen Mar. 2, 1943 2,500,167 Garwood Mar. 14, 1950 2,522,512 Harman Sept. 19, 1950 FOREIGN PATENTS 616,521 Great Britain Jan. 24, 1949 

1. AN ADDITIVE FOR MINERAL LUBRICATING OIL CONSISTING ESSENTIALLY OF AN OIL SOLUBLE ISOBUTYLENE -BUTADIENE-HYDROGEN SULFIDE POLYMER CONTAINING 0.5-15 WEIGHT PERCENT SULFUR, HAVING AVERAGE MOLECULAR WEIGHT BETWEEN ABOUT 2000 AND ABOUT 7000, AND PREPARED BY POLYMERIZING, IN A REACTOR WITH FRIEDEL-CRAFTS CATALYST, FROM 2-20 MOLS OF ISOBUTYLENE WITH A MOL OF BUTADIENE AND ABOUT 0.05 TO ABOUT 0.8 MOL OF HYDROGEN SULFIDE PER OLEFINIC DOUBLE BOND IN SAID HYDROCARBON REACTANTS AS FED TO THE REACTOR. 